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      1 /*
      2  * Copyright (C) 2010 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1.  Redistributions of source code must retain the above copyright
      9  *     notice, this list of conditions and the following disclaimer.
     10  * 2.  Redistributions in binary form must reproduce the above copyright
     11  *     notice, this list of conditions and the following disclaimer in the
     12  *     documentation and/or other materials provided with the distribution.
     13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
     14  *     its contributors may be used to endorse or promote products derived
     15  *     from this software without specific prior written permission.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
     18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
     24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include "config.h"
     30 
     31 #if ENABLE(WEB_AUDIO)
     32 
     33 #include "Distance.h"
     34 
     35 #include <algorithm>
     36 #include <math.h>
     37 
     38 using namespace std;
     39 
     40 namespace WebCore {
     41 
     42 DistanceEffect::DistanceEffect()
     43     : m_model(ModelInverse)
     44     , m_isClamped(true)
     45     , m_refDistance(1.0)
     46     , m_maxDistance(10000.0)
     47     , m_rolloffFactor(1.0)
     48 {
     49 }
     50 
     51 double DistanceEffect::gain(double distance)
     52 {
     53     // don't go beyond maximum distance
     54     distance = min(distance, m_maxDistance);
     55 
     56     // if clamped, don't get closer than reference distance
     57     if (m_isClamped)
     58         distance = max(distance, m_refDistance);
     59 
     60     switch (m_model) {
     61     case ModelLinear:
     62         return linearGain(distance);
     63         break;
     64     case ModelInverse:
     65         return inverseGain(distance);
     66         break;
     67     case ModelExponential:
     68         return exponentialGain(distance);
     69         break;
     70 
     71     default:
     72         return 0.0;
     73     }
     74 }
     75 
     76 double DistanceEffect::linearGain(double distance)
     77 {
     78     return (1.0 - m_rolloffFactor * (distance - m_refDistance)) / (m_maxDistance - m_refDistance);
     79 }
     80 
     81 double DistanceEffect::inverseGain(double distance)
     82 {
     83     return m_refDistance / (m_refDistance + m_rolloffFactor * (distance - m_refDistance));
     84 }
     85 
     86 double DistanceEffect::exponentialGain(double distance)
     87 {
     88     return pow(distance / m_refDistance, -m_rolloffFactor);
     89 }
     90 
     91 } // namespace WebCore
     92 
     93 #endif // ENABLE(WEB_AUDIO)
     94